Fix eslint violations for ES UI Global flyout

Supports https://github.com/elastic/kibana/issues/49554

```
/kibana/src/plugins/es_ui_shared/__packages_do_not_import__/global_flyout/global_flyout.tsx
  163:6  error  React Hook useEffect has a missing dependency: 'getContents'. Either include it or remove the dependency array  react-hooks/exhaustive-deps
```